Table salt is NOT sodium nitrate! Both sea salt and table salt are sodium chloride. Sodium nitrate is entirely different; it's used as a preservative in some processed meats and occurs naturally in vegetables, but it's not something you're going to have on your table.
Sea salt and table salt are produced differently and have different advantages/disadvantages in cooking, but there's very little difference in their effect on your health. Table salt is finer, so more of it fits into a teaspoon measure, and that has led some people to say it "has more sodium." By weight, though, they're the same.
Here's the Mayo Clinic website's comment on sea salt vs. table salt: www.mayoclinic.com/health/sea-salt/an01142